Liquid level measuring systems using magnetic sensors are commonly used to measure the level of a liquid, such as oil, in a tank or container. Early versions of these liquid level sensors used sensors that could detect a magnetic field. By determining which sensor has detected the magnetic field created by a float, the liquid level sensor can approximate the level of liquid. However, the accuracy of this level determination often required the sensors to be quite close together or the magnetic float to be a complicated system of magnets to try and increase the accuracy of the depth approximation.
Some later liquid level sensors, such as the system described in U.S. Pat. No. 5,636,548 to Dunn et al, used hall-effect sensors that could produce an analog output signal in response to the sensors coming into contact with a magnetic field from a float. This allowed the depth of the liquid in the tank or container to be approximated with greater accuracy, however, it required extensive calibration of the system to provide these readings. In this system, the float must be moved relative to each sensor to determine the voltages corresponding to each position of the float relative to the sensor to calibrate the system for use. This calibration may also become less accurate as the measuring system and its sensors age. It also requires specific numbers of sensors and spacing between the sensors requiring the system to be designed for a specific size of tank or container. Thus, while these systems have increased accuracy, they require extensive calibration and must be designed quite specifically for the intended tank or other application for the system to function properly.